Understanding the productivity of cassava in West Africa

Abstract

Drought stress and sub-optimal soil fertility management are major constraints to crop production in general and to cassava (Manihot esculenta Crantz) in particular in the rain-fed cropping systems in West Africa. Cassava is an important source of calories for millions of smallholder households in sub-Sahara Africa. The prime aim of this research was to understand cassava productivity in order to contribute to improving yields, food security and farm incomes in rain-fed cassava production systems in West Africa. A long-term goal was to contribute to a decision support tool for site-specific crop and nutrient management recommendations. Firstly, we studied farmers' perception of cassava production constraints, assessed drivers of diversity among households and analysed the suitability of farmers' resource endowment groups to the intensification of cassava production. The results indicate that farmers perceived erractic rainfall and poor soil fertility to be prime constraints to cassava production. The agricultural potential of the area and the proximity to regional markets were major drivers for the adoption of crop intensification options including the use of mineral and organic fertilizers. While the use of mineral and organic fertilizers was common in the Maritime zone that had a low agricultural potential, storage roots yields were below the national average of 2.2 Mg dry matter per hectare, and average incomes of 0.62, 0.46 and 0.46 US$ per capita per day for the high, medium and low farmer resource groups (REGs -HRE, MRE and LRE, respectively) were below the poverty line requirement of 1.25 US$. In the high agricultural potential Plateaux zone, HRE and MRE households passed this poverty line by earning 2.58 and 2.59 US$ per capita per day, respectively, unlike the LRE households with 0.89 US$ per capita per day. Secondly, we investigated the effects of mineral fertilizer on nutrient uptake, nutrient physiological use efficiency and storage roots yields of cassava since soil fertility was a major issue across the zones. We used an approach based on the model for the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS). This model was successfully adapted for cassava and it appropriately assessed the response of cassava to N, P and K applications, especially in years with good rainfall. Under high drought stress, the model overestimated cassava yields. Thirdly, we investigated the impact of balanced nutrition on nutrient use efficiency, yield and return on investment compared to blanket fertilizer use as commonly practiced in cassava production systems in Southern Togo, and in Southern and Northern Ghana. The balanced nutrition approach of the QUEFTS model aimed to maximize simultanously nutrient use efficiency of N, P and K in accordance with the plant's needs. Larger nutrient use efficiencies of 20.5 to 23.9 kg storage root dry matter (DM) per kilo crop nutrient equivalent (1kCNE of a nutrient is the quantity of that nutrient that has the same effect on yield as 1 kg of N under balanc...

Effect of Chicken Manure Application on Cassava Biomass and Root Yields in Two Agro-Ecologies of Zambia

“…Because farmers can obtain roots for their subsistence from cassava planted on very marginal fields [56][57][58], a low-to-no input farming system is preferred compared to an input-intensive farming system for cassava. The slash and burn system that is still practiced by some Zambian farmers, especially in the Northern part of the country [59], could also explain the observed low fertilizer use in Zambia.…”

“…The slash and burn system that is still practiced by some Zambian farmers, especially in the Northern part of the country [59], could also explain the observed low fertilizer use in Zambia. However, as evidenced in West and East African countries [56,58,60], a low input production system cannot support the high crop yield required to meet the needs of a growing population and can also cause environmental degradation, through deforestation and carbon dioxide emissions. Therefore, these conditions necessitate the use of fertilizer, either organic or mineral sources, to sustain cassava farming in the long run and meet the growing cassava demand in the country.…”

Growing out of hunger: towards an improved understanding of the water and nutrient limited yield of cassava

“…The largest cassava yield of 35 t DM ha -1 at 14 MAP was achieved in Edo, equivalent to 97 t ha -1 of fresh storage roots. No effects of drought were observed in 2016 for Edo, despite a brief dry season, due to the rooting depth of cassava in this field, which was greater than 3.2 m. This observed yield is larger than the target yield of 90 t ha -1 of fresh roots which we used to determine the nutrient requirements with the QUEFTS model (Ezui, 2017). These yields are comparable to the simulated ideal yield of 32 t DM ha -1 at 12 MAP proposed by Cock et al (1979) and to the actual recorded yields of 27 -32 t DM ha -1 at 10 MAP reported from Cauca, Colombia (El-Sharkawy et al, 1990).…”

“…Treatment names are as shown in Table 2.2, where (f) represents full rate of the optimized nutrient and K60, K120, K180, K240, were varied at rates of K at 60, 120, 180 and 240 kg ha -1 (Table 2.2). The optimized fertilizer rates and combinations for the experimental treatments were determined using the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model for cassava (Ezui, 2017), aiming at a yield of 90 t fresh roots ha -1 (equivalent to 32 t DM ha -1 ). Cassava variety TME 419 was grown in all experiments: this is a popular variety in Nigeria and West Africa because it has high dry matter and is nutrient use efficient (De Souza and Long 2018).…”

“…Results from on-station and on-farm researcher-managed trials in the region have shown that cassava yield can be improved substantially with improved crop establishment, genotype and management. Root yields up to 19 t DM ha -1 (equivalent to 54 t ha -1 of fresh roots) were recorded in on-farm trials with fertilizer application in Southern Togo within 10 to 11 months after planting (Ezui, 2017). Fresh root yields of 40 t ha -1 were attained with improved varieties in on-station trials in Nigeria (Eke-Okoro and Njoku, 2012).…”